Packaging machine



Nov. 17, 1970 A. PARVINV ET-AL 3,540,186

PACKAGING MACHINE Filed March 11, 1968 15 Sheets-Sheet 1 FIG. lB

INVENTORS ALLAN l. PARVIN Bl DOUGLAS P. ROOME their ATTORNEYS Nov. 17., 1970 A. I. PARVIN ETAL PACKAGING MACHINE 15 Sheets-Sheet 2 Filed March 11, 1968 qw at INVENTORS & S M v! m0 E VM M m. f m PP T I S A A fi/ A LU r 5 4m AD m 5 1970 A. l. PARVIN ET AL $540,1 8 PACKAGING MACHINE Filed March 11, 1968 15 Sheets-Sheet 4 INVENTORS ALLAN l. PARVIN 8n DOUGLAS P. ROOME their ATTORNEYS 'NOV- 1970 A. l. PARVIN ETAL 3,54

PACKAGING MACHINE Filed March 11, 1968 15 Sheets-Sheet 5 mvmwmus ALLAN l. PARVIN a M DOUGLAS P. ROOME their ATTORNEYS Nov. 17., 1970 1. P VI ETAL 3,540,186

PACKAGING MACHINE Filed March 11, 1968 5 Sheets-Sheet v INVENTORS ALLAN l. PARVIN 8 BY DOUGLAS R ROOME their ATTORNEYS Nov. 17, 1970 A. l. PARVIN E L PACKAGING MACHINE 15 Sheets-Sheet 9 Filed March 11, 1968 mm m EM INVENTORS PARVIN 8| DOUGLAS P. ROOME ALLAN I.

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A T TORNEYS their Nov. 17, 1970 A. l. PARVIN ETAL 3,540,186

PACKAGING MACHINE Filed March 11, 1968 15 Sheets-Sheet 1O vENToRs PARVIN a E Sw a E X ,a fiwww m;

their ATTORNEYS N66. 17., 1970 A. I. PARVIN ET AL 31540186 PACKAGING MACHINE 15 Sheets-Sheet 11 Filed March 11, 1968 RM 3 m INVILN'IORS ALLAN l. PARVIN DOUGLAS P. ROOME I%-/IJ%-IZ- their BY J A TTORNEYS Nov. 17, 1970 A. 1. PARVIN ETAL 3,540,186

PACKAGING MACHINE INMENTORS ALLAN I. PARVIN 8x DOUGLAS P. ROOME their A TTORNEYS I Nov. 17., 1970 A. l. PARVIN ETAL 3,540,186

PACKAGING MACHINE Filed March 11, 1968 15 Sheets-Sheet 13 INVEN'I'URS ALLAN I. PARVIN a Y DOUGLAS P. ROOME then ATTORNEYS Nov. 17., 1970 PARVlN ETAL 3,540,186

4 PACKAGING M'ACHINE Filed March 11, 1968 15 Sheets-Sheet 14.

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INVENTORS ALLAN l. PARvm 5 BY DOUGLAS P. Rooms their ATTORNEYS Nov. 17, 1970 A. I. PAR-VIN ETAL PACKAGING MACHINE Filed March 11 1968 15 Sheets-Sheet 15 .&E R M m mwm v mmpfl/ LS A ML 2% LU LO AD% YA M av their 3,540,186 PACKAGING MACHINE Allan I. Parvin, Milburn, and Douglas P. Roome, Cedar Grove, N.J., assignors to Standard Packaging Corporation, New York, N.Y., a corporation of Virginia Filed Mar. 11, 1968, Ser. No. 712,209 Int. Cl. B65b 31/04, 41/18, 57/02 US. Cl. 53-51 13 Claims ABSTRACT OF THE DISCLOSURE A packaging machine for applying cover sheets to substantially rigid, product-containing trays and evacuating and sealing the covered trays. The product-containing trays are moved in succession along a conveyor at a substantially uniform speed, and a cover web is tack-sealed to the leading edge of each tray. As each tray moves along a conveyor, it draws the cover web over it, the web is severed at the trailing edge, and an initial seal is then formed between the cover sheet and tray. Next, the tray is evacuated through openings left in the initial seal between the cover sheet and the tray and final seats to close the evacuation openings are made.

This invention relates to a novel and improved packaging machine for making evacuated packages.

Patent application Ser. No. 645,387, filed June 12, 1967, for Air Evacuated Package, which is assigned to the assignee of this application, discloses a package which includes a tray having a pair of product-receiving pockets and a pair of spaced-apart slits defining a defiectable strip. A cover film is preliminarily heat-sealed to the tray about the perimeters of the pockets, except in the regions adjacent the slits, and the product-receiving pockets are evacuated through passages created by holding the defiectable strip and the overlying portion of the cover film away from the plane of the tray. Thereafter, the remaining parts between the perimeter of each pocket and the slits are heat-sealed to completely close the package.

The packaging machine, in accordance with this invention, is an improvement over presently known packaging machines and is suitable for forming the packages disclosed in the application identified above. It comprises a conveyor for transporting product-containing trays along a predetermined path at a substantially constant speed, the conveyor including a series of tray carriers which are provided with recesses so that the trays are nested firmly therein. The filled trays are deposited on the carriers and are moved along to a pressing unit for compacting the product tightly into the tray pockets and ensuring that the product lies entirely below the plane of the tray flanges. The pressing unit moves back and forth longitudinally in timed relation to the movement of each try, and the pressing operation is carried out as each tray moves along on the conveyor. A pressing unit is often desirable for packaging slide luncheon meats, cheeze, bacon and similar products, but it is an optional feature and may not be needed with some products.

After the pressing operation, each tray is carried to a United States Patent 3,540,186 Patented Nov. 17, 1970 web supply unit which delivers the leading edge of a cover web into aligned relation with the leading edge of each tray. The supply unit includes apparatus for securing the free end of the web on the leading edge of the tray, the web being pulled out by the tray upon its further movement with the conveyor. For this purpose, a heated tack seal bar is provided immediately downstream of the web supply for heat sealing the leading end of the web to the tray. After each tray has moved further along on the conveyor, the trailing edge of the Web is severed adjacent the trailing edge of the tray by a cutting blade.

Often, the cover Web will be printed with a label, and it should therefore be deposited in accurate registration with the tray. Registration of the Web is accomplished by pulling it back to a predetermined extent before tacking the leading edge to the next following tray immediately after severing from the end of the preceding tray. More particularly, apparatus is provided for gripping the web, pulling it back, and then terminating the pulling back when indicia printed on the web passes a certain point. This indicia may be a special mark or a part of the label, and pull back of the web may be terminated, upon a control signal from a photocell detector, by releasing the gripping mechanism holding the Web. The leading edge of the web is then tacked to the leading edge of the next tray as it moves into position.

The tray moves next to an initial sealing unit which is moved into engagement with the cover film and includes sealing bars for forming heat seals about the perimeters of the tray pockets, except for the regions between the slits in the tray and the tray pockets. When the initial or preliminary seal has been made, the unit is moved out of engagement with the tray.

The tray moves along on the conveyor to an evacuating and final seal unit which is moved into operative position and creates a closed chamber containing the package unit. An evacuating head is coupled to the chamber, and communication is established to the pockets by a member provided on each tray carrier for holding the deflectable strip in the tray and the portion of the cover film adjacent the strip away from the tray surface to communicate an evacuating head moved into engagement with the carrier with the interiors of the tray pockets for evacuation of the package. If desired, the package may be refilled with an inert gas. A final heat seal bar in the unit is then moved into engagement with the cover film to complete the heat seals around the perimeters of the tray pockets by sealing the cover to the tray in the regions between the pockets and the slits not previously sealed by the initial seal unit.

All of the machine operations, except the feeding-in of the web, are accomplished by mechanisms which, during their operations, move forward conjointly with the package units upon which they are operating. Upon completion of its function, each of the operating devices is then moved back into position in readiness for the next following package unit. It will be noted, therefore, that all of the operations are performed by the machine without ever stopping the movement of the tray, the conveyor moving at a substantially uniform rate.

Preferably, synchronization between the functions of the several units and the movement of the conveyor is ensured by providing a common drive for the conveyor and for the mechanism which moves the operating units back and forth along the path of movement of the conveyor. By performing all of the operations while the trays are in movement, the time lost in starting and stopping the conveyor and moving it between the operating stations, as is the case with a number of types of presently known packaging machines, is eliminated, thereby considerably enhancing operating speed.

For a better understanding of the invention, reference may be made to the following description of an exemplary embodiment, taken in conjunction with the figures of the accompanying drawings, in which:

FIG. 1A is a pictorial view of a top of a finished package formed by the machine of the invention;

FIG. 1B is a bottom pictorial view of the package of FIG. 1, the defiectable strip being shown in a lifted position enabling evacuation of the interior;

FIGS. 2A, 2B and 2C are side views in section showing, when taken together, the complete machine, the sections all being taken along planes immediately inside the nearside frame of the machine;

FIG. 3 is a side view in section, on a larger scale than FIG. 2, showing details of an input conveyor utilizable with the machine of the invention;

FIG. 4 is an end view in section of the machine, taken generally along the line 44 of FIG. 2B and in the direction of the arrows and being on a larger scale than FIG. 2B, which shows the pressing unit of the machine;

FIG. 5 is an end view in section showing the cover web supply mechanism, the view being taken along the line 5-5 of FIG. 2B, in the direction of the arrows and on a larger scale;

FIG. 6 is a side elevational view showing the details of a cover web pull-back mechanism, the view being on a larger scale than FIG. 2B;

FIG. 7 is a view in section of a portion of the pull-back mechanism illustrated in FIG. 6, the view being taken generally along the line 7-7 of FIG. 6 and in the direction of the arrows;

FIG. 8 is an end view in section of the tack seal mechanism, the view being taken generally along the line 8-8 of FIG. 2B, in the direction of the arrows, and on a larger scale than FIG. 2B;

FIG. 9 is a side elevational view of the tack seal mechanism and the cover web cutting bar on a larger scale than FIGS. 2B and 2C;

FIG. 10 is a side elevational view similar to FIG. 9 but showing certain parts of the mechanisms in section and showing them at a difierent stage of operation;

FIG. 11 is a top view of the tack seal unit shown in FIGS. 9 and 10;

FIG. 12 is an end view in section showing the initial seal head and the cover web cutting blade, the view being taken generally along the line 1212 of FIG. 2C, in the direction of the arrows and on a larger scale than FIG. 20;

FIG. 13 is an end view in section of the evacuating and final seal head of the machine. the view being taken generally along the line 13-13 of FIG. 2G, in the direction of the arrows and on a larger scale;

FIG. 14 is a side view in section of the evacuating and final seal head, the view being taken generally along the centerline plane; and

FIG. 15 is an end view of a portion of the actuating mechanism for the initial seal head and the evacuating and final seal head of FIG. 2C, the view being taken along a plane indicated generally by the lines 1515 of FIG. 2C, in the direction of the arrows, and on a larger scale.

It will be understood in the course of the following description that in the drawings, parts of the machine are broken away in places or omitted in some views for clearer illustration. In addition, different figures sometimes show the same parts at different stages of operation.

Referring to FIGS. 1A and 1B, the packages made up by the packaging machine of the invention comprise a relatively rigid plastic tray having a pair of spaced- 4 apart product-receiving pockets 22. The particular trays illustrated in the drawings are shaped to receive sliced bacon 24 laid out in the conventional overlapping manner. In the space between the pockets 22 is a pair of spacedapart slits 26 which define a defiectable strip 28.

Overlying the tray and secured to it by means of heat seals 30 about the perimeters of each of the pockets 22 is a cover film 32 of transparent plastic. The heat seals 30 are formed in two stages and consist of initiallyformed portions, referred to herein as initial seals and designated 30a in the drawings, and finally formed portions, or final seals designated 30b in the drawings. The initial seals 30a extend from adjacent one end of each slit and about the perimeter of the tray pocket 22 nearest that slit and terminate near the opposite end of that slit, thereby leaving openings for communicating the tray pockets with a vacuum source. The interiors of the tray pockets are evacuated through these openings by holding the deflectable strip and the overlying part of the cover away from the plane of the tray surface. Thereafter, the final seals 30b, which extend between and overlap the ends of the initial seals 30.. are formed to completely close the package. In FIG. 1A, the initial seals 30a are indicated by cross-hatching from upper right to lower left and the final seals 3011 by cross-hatching from upper left to lower right.

As mentioned previously, the cover films are applied to the trays by first securing the leading edge of a web to the leading tray flanges by tack seals and then permitting the trays to pull the web into overlying relation over them as they are transported by the conveyor. The tack seals are designated by reference numeral 34 in the drawings and are shown as being spaced from the adjacent portions of the preliminary seals 30a, but it will be understood that the tack seals 34 may be coincident with portions of the initial seals 30a and merged into the initial seals when they are later formed.

The package itself forms no part of the present invention, being the subject matter of the copending application mentioned above; however, the above brief description will be helpful in facilitating an understanding of the packaging machine of the invention, and reference will be made herein to elements of the package from time to time.

The trays 20, which may be purchased by the packager or may be formed by the packager by suitable apparatus in association with the packaging machine, are filled with the product and delivered to the packaging machine by a delivery conveyor 40, which is illustrated in FIGS. 2A and 3. For example, apparatus is available for weighing and loading measured amounts of sliced bacon in the conventional overlapping form into the trays. From this apparatus, the loaded trays may be dropped onto a platform 42, as illustrated in FIG. 3, and thereafter removed from the platform and deposited on the conveyor belt 44.

For the purpose of providing a sufficient number of loaded trays to utilize a full capacity of the packaging machine of the invention, it may be necessary to use two or three loading and weighing machines. To this end, the delivery conveyor (FIG. 3), may include a series of transverse bars 46, which are spaced-apart longitudinally and carry slidably mounted pins 48. The platforms 42 include slots through which the pins 48 can move, and below each of the platforms is a pair of earns 50. The pins 48 are normally held in a lower position by a spring 52. The specific arrangements of the pins 48 will vary, depending upon the number of weighing and loading machines used, but assuming as an example that there are three loading and weighing machines supplying the packaging machine, every third pair of pins 48 will be positioned in the same location and will be actuated by cams 50 located below the platform of one of the weighing and loading machines. The intermediate pins will be positioned differently and will be actuated by correspondingly positioned cams on each of the other two loading machines. Thus, a tray on each of the three weighing and loading machines is engaged by a respective pair of pins 48 on each of every three conveyor sections in succession and is pushed off the platform onto the conveyor 44.

Referring to FIG. 2A, the trays 20 are delivered by the input conveyor to an overhead flight conveyor 60, which includes a pair of spaced-apart slides 62 and a chain 64 carrying a series of pusher bars 66. The trays are pushed by the bars 46 on the conveyor 40 onto the slides 62 which support them along their flanges, and they are engaged by the pusher bars 66 and moved along into position in one of the tray carriers 68 of a main transport 70. i

As illustrated in FIGS. 2A, 2B and 2C, which taken together from right to left in the order given make up a complete side view of the machine, the transport conveyor 70 includes a continuous series of spaced-apart tray carriers 68 coupled together in a train and moved along a horizontal path by a pair of sprocket driven chains 72. As shown in FIG. 4, for example, the carriers 68 are located between the two chains 72 and, when traversing the upper side of the conveyor, are supported on a pair of spaced-apart, longitudinally extending tracks 74 by rollers 76. Similarly, the chains 72 during the major portions of horizontal movement are supported by longitudinally extending members. As illustrated in FIG. 2C, the chains are carried at one end and are driven by a pair of main drive sprockets and, as shown in FIG. 2A, are carried at the input end by idler sprockets 82. The conveyor is driven at a substantially constant, uniform speed and, as indicated by the arrows in FIGS. 2A, 2B and 2C, from right to left.

Referring to FIG. 4, the tray carriers 68 are formed with recesses, illustrated by dotted lines, corresponding substantially to the shapes of the tray pockets 22 so that the trays nest snugly in them. Referring briefly back to FIG. 2A, the flight conveyor 60 slopes downwardly toward the delivery point so that the leading edge of the tray pockets enter smoothly into the recesses of the tray carriers at the urging of the pusher bars 66. The desired sliding movement and angle of approach to the carriers may be provided by adjusting the angular position of the conveyor 60.

Each of the trays is carried, first of all, to a pressing station. When the trays are filled with certain products, particularly sliced bacon, it is possible that the upper portions of the product will lie above the plane of the upper surface of the tray and, further, that the product will not be well-compacted or well-fitted into the tray pockets. At the pressing station is a pressing unit 88 which presses and compacts the product firmly into the tray pockets and makes certain that the product lies entirely below the plane of the tray flanges. The pressing unit is shown to the right in FIG. 2B, and an end view is contained in FIG. 4.

The pressing unit includes a carriage 90 mounted above the conveyor for movement parallel to the line of movement of the conveyor by means of rollers 92 on opposite sides which roll in tracks 94 on the machine frame. The carriage is moved longitudinally back and forth by a chain arrangement. More particularly, the right end of the carriage 90, with respect to FIG. 2B, is connected by a short length of chain 96 to a sprocket 98 carried on a rotatable transverse shaft 100. The chain 96 wraps around the sprocket 98 and is connected to it by a coupling 102. On one end of the shaft 100 outside the main machine frame is another sprocket 104 having a chain section 106 wrapped around and secured to it. The chain section 106 passes along the outside of the machine, as shown in FIG. 2B, and around idler sprockets 108 and 110 and is secured at its other end by a connector 112 to a reciprocating bar 114, which will be described in greater detail hereinafter.

Another chain 116 is attached near the center of the left end of the carriage 90, with respect to the view of it in FIG. 213, extends parallel to the path of movement of the conveyor, passes around a sprocket 118 and leads outwardly to the same side of the machine as the chain 106. The chain 116 then passes around another sprocket and passes toward the output end of the machine where it is connected to the connector member 112. Upon reciprocating movement of the bar 114, the chains 106 and 116 move therewith in a manner to produce corresponding reciprocation of the carriage 90 back and forth in a direction parallel to the movement of the conveyor.

Mounted for vertical movement in the carriage 90 is a pair of pressing members 120, one for each of the two pockets 22 in the trays. Each of the pressing members comprises a support element 122 having an upwardly extending arm 124, and a pressing head 126 which is carried by spring mountings on the support element 122. The element 122 is normally held in an upward position relative to the carriage 90 by four spring mountings 128, the four separate spring mountings affording compressing of the product, such as bacon strips, into the tray pockets by relatively uniform pressure.

Above each of the pressing members is an actuating mechanism for moving the pressing heads downwardly to press the bacon strips into the tray pockets. The mechanisms for each of the two pressing assemblies 120 are the same and include a cam bar 130 which is pivotally mounted at one end on a shaft 132 installed in a pair of longitudinally extending, adjustable frame members 131, the members 131 being adjustable to enable the extent of pressing of the press to be set to a predetermined magnitude. The cam bar is urged upwardly at the other end by a spring 134. A link 136 is attached at one end to a bracket 138 secured to the carriage 90 and at the other end to the upwardly extending arm 124 on the pressing member element 122. The upper end of the link 136.carries a cam follower in the form of a roller 140 which engages and rides along the lower surface of the cam bar 130.

When the press unit is in approximate position shown in FIG. 2B, it is in readiness for a pressing operation, which is to be performed on the tray directly below it at that time. In this position, a cam stop pin 142 holds the cam bar 130 in an operative position. The stop pin 142 is operated by a pneumatic cylinder 144 and slides through openings in the cam bar mounting frame members 131.

As the carriage and the pressing members are moved forward by the reciprocating rod 114 acting through the chain drive, the cam followers 140 move along the lower surfaces of the cam bars 130 and cause the links 136 to urge the pressing members downwardly and to press the bacon into the tray pockets. Near the end of the forward movement movement of the press unit, the air cylinder is operated to withdraw the cam engaging pin 142 from the position in which it holds the cam bar down so that the carnbar 130 is released and is withdrawn upwardly by its spring 134. As a result, the pressing members are released, and their retracting springs 128 pull them upwardly out of engagement with the bacon. The forward movement of the carriage and pressing units is, of course, in synchronization with the movement of the conveyor. After the retraction of the pressing members, the carriage is moved back by the rod 114 into position to operate on the next tray.

The retraction or backward movement of the press unit also accomplishes the resetting of the cam bars for the next pressing operation. More particularly, each cam bar carries a reset arm 146 which is engaged by the cam follower 140 near the end of the retracting movement of the carriage and pivots the cam bar 130 back into operating position, whereupon the air cylinder 144 is actuated to move the cam stop pin 142 back into engagement with the cam bar.

As shown in FIG. 4, a bracket assembly 150 extends from a fixed mounting member 152 secured on the carriage 90. The bracket assembly 150 includes a vertical member 154 which is alfixed to a shaft 156 pivotally mounted in the mounting member 152. Pivotally attached to the lower end of the vertical member 154 are support arms 158 and 160 which extend inwardly between the upper and lower traverses of the conveyor and carry a vacuum hold-down assembly 162. The hold-down assembly includes a support bracket 164 which carries a pipe 166 having a flange and gasket 168 at the upper end. The pipe 166 is urged upwardly by a spring 169 and is coupled to a conduit 170.

As shown in dotted lines in FIG. 4, the tray carriers 68 of the conveyor are provided with channeling 172 and a passage 174 which communicates the recesses in the carrier with the pipe 166 when the pipe flange and gasket 168 are in engagement with the lower surface of the carrier 68. The conduit 170 is connected to a vacuum source, and a subatmospheric pressure is created in the recesses of the carrier 68 to provide a hold-down force on the trays and ensure that they will not be lifted out of the carriers when the pressing unit is withdrawn after the pressing operation.

The hold-down assembly 162, because it is bracketed from the carriage 90, moves conjointly with the conveyor carriers 68 during the pressing operation. In synchronization with that movement, the hold-down assembly 162 is moved upwardly by a lift bar 176 into operative engagement with the carriers. A roller coupling 178 attached to the lower mounting arm 160 of the hold-down unit mounting bracket slides longitudinally along the bar 176. As shown in FIG. 2B and also to the left in FIG. 2A, the lift bar 176 is carried on crank arms 180 mounted on transverse shafts 182, and a longitudinally extending actuating bar 184 is coupled to the crank arms and is moved longitudinally by a cam mechanism 186 (FIG. 2B). In proper synchronization with the forward movement of the carriage 90 and the hold-down assembly 162, the actuating bar 184 is moved to the right by the cam 186, thereby causing the crank arms 180 to lift the lift bar 176. Accordingly, the roller coupling 178 is moved upwardly, thereby lifting the arm 160 and correspondingly moving the hold-down assembly 162 into engagement withthe bore 174 in the carrier 68. At the same time, a vacuum pressure is communicated through the conduit 170 to the recesses in the carrier and provides a hold-down force due to the pressure differential on the trays 20.

From the pressing unit, the trays, in which the product is now compacted and lies entirely below the plane of the tray flanges, are transported to a cover web delivery and tack seal unit 200, which is shown in FIGS. 2B and to 10. Briefly, the unit 200 includes a web supply mechanism 202 which draws the cover web 204 from a supply roll 206, a pull-back mechanism 208, which ensures that registration between any printing on the cover web 204 and the trays is maintained, and a tack seal mechanism 210, which secures the leading edge of the web to the leading edge of the trays by the tack heat seals 34 (FIG. 1A). The tack seals enable the web to be pulled out into overlying relation over the trays where it is later severed adjacent the trailing edge of the tray. The pullback mechanism 208 operates to pull the severed end, which is now the leading end of the Web, back a short distance so that it overlies the leading edge of the next following tray.

In the web supply 202, as shown in FIGS. 2B and 5, the web 204 is led from the supply roll 206 over an idler roll 212 and between the rolls of a three roll drive unit 214, under an idler roll 218, over a dancer roll 216 and under an idler roll 220. The elements of supply mechanism 202 and also the pull-back mechanism 208, are mounted in fixed end frame plates 222 and 224 attached at opposite sides of the packaging machine main frame. The drive unit 214 is driven by a chain 226 through a transmission which includes a magnetic clutch 228 and brake 230. In its uppermost position, the dancer roll arm 217 engages a microswitch 232 which disengages the 8 clutch 228 and applies the brake 230 to temporarily stop the removal of the cover web 204 from the supply roll. When the dancer arm is pulled down as the cover web loop around it is used, the clutch is engaged and the brake released so that positive feed of the web is commenced again. The range of movement of the dancer roll is limited by stops 234 and 235.

The web passes from the idler roll 220 over a rubber gripping roll 240, over an idler roll 242 and then downwardly to the tack seal head. Referring to FIGS. 5, 6 and 7, the gripping roll 240 is carried by a pair of mounting plates 244 and 245 fixed to a shaft 246 which is pivotally mounted in the frame members 222 and 224. The shaft 246 is pivoted to provide back and forth movement of the plates 244 and 245 by a cam follower 248 which rides in a chain driven cam 250.

The mounting plates 244 and 245 carry a mechanism for engaging the web immedaitely after it is severed adjacent the trailing edge of a tray and pulling it back to a predetermined extent so that it is in proper registration with the next following tray on the conveyor. More particularly, a shaft 252 extends transversely across the machine and is pivotally mounted in the members 244 and 245. Afiixed to the shaft 252 is a gripping head 254 which is positioned to selectively move into engagement with the web and hold it against the roll 240. The shaft carries a fixed arm 256. A pin 258 on the end of the arm 256 slides in a slot 260 in a lever 262 which is pivotally attached to the plate 244 by a bolt 264. The lever 262 includes a generally horizontally extending portion 262a and a generally vertically extending portion 262b. At the end of the horizontal portion 262a is a roller 268 which cooperates with a roller 270 afiixed at the upper end of a lever 272. The lever 272 is pivotally mounted on a bolt 274 fastened to the plate 244. Also pivotally mounted on the bolt 274 is a lever 275 which is coupled to a solenoid 27-6 and carries an element 278 having a pin positioned to engage the lower end of the lever 272.

Attached to the side frame members 222 and 224 of the unit 200 is a pneumatic cylinder 280 which operates a reset pin 282, and attached to the mounting plate 244 is a stop member 284. When the gripping head 254 is disengaged from the roll 240, as shown by the phantom view thereof in FIG. 6, the vertical portion 262b of the lever 262 rests against the end of the stop 284, being urged into this position by a spring 286 which holds the gripping head 254 out of engagement with the web and roll 240 and also retains the arm 256 in its clockwise-most position, with respect to the view of it in FIG. 6. At the same time, the solenoid 276 holds the lever 272 in its clockwise-most position (also shown in phantom view in FIG. 6) so that the pin 270 lies generally horizontally adjacent the pin 268 at the end of the horizontal portion 262a of the lever 262. This is generally the position of the gripping mechanism just after the mechanism has been released after completing an operation, and at this time, the mounting plates 244 and 245 are at or near their clockwise-most position.

Starting in this position, the cam 250 is still pivoting the mounting plates counterclockwise. The reset pin 282 is now moved outwardly by the cylinder 280, and when the upper end of the vertical portion 262b of the lever 262 engages the pin 282, the lever 262 is pivoted clockwise about its mounting 264, thereby forcing the arm 256 counterclockwise and the gripping head 254 into engagement with the web and with the roll 240. This will occur just after the web has been severed along the trailing edge of a tray which has advanced from the tack seal position. When the gripping head 254 is in clamping engagement with the web and the lever 262 is in its clockwisemost position, a spring 299 attached to the lever 272 pivots it counterclockwise into a position, as shown in FIG. 7 and in solid lines in FIG. 6, in which the pin 270 is located above the pin 268 and the lever 262 is held in a position to retain the gripping element 254 in engagement with the web and roll 240.

Immediately after the gripping head engages the web, the cam 250 starts clockwise pivoting of the mounting plates 244, thereby pulling the web 204 back. The web is pulled back until it is positioned in registration with the tray which is then moving into position for tacksealing of the web to it. Registration of the cover web with the trays is maintained by releasing the web to terminate the pull-back operation as soon as a special mark printed onto the web or a certain part of the label is detected by a photocell control unit 300 ('FIGS. 2B and 5) mounted on the web supply unit. When the marks on the web pass a photocell detector in the unit 300, the signal produced is conducted to the solenoid 276 and energizes it to pivot the lever 275 clockwise. This in turn pulls the lever 272 in a direction to remove the pin 268 on the lever 262 out of holding engagement with the pin 270, releasing the lever 262 and permitting the spring 286 to pull the gripping element upwardly to release the web. This completes one cycle of operation of the pull-back mechanism, and it is now in readiness for the next cycle.

The web 204 passes from the idler roll 242 around a series of three tension rolls 310, 311 and 312 and is fed into the tack seal unit 314, which is shown in FIGS. 8 to 11. The tack seal unit includes a carriage 316 comprising end members 318 and 319, a top member 320, a vertical front wall member 322 and a cross member 324 carried by brackets 325. The carriage is mounted for longitudinal movement along the main machine frame by rollers 326a and 326b which roll in longitudinally extending tracks 328a and 32% mounted on the machine frame.

Journaled in and extending transversly between the end members 318 and 319 is a shaft 330. Arms 332, which carry a transversely extending web guide strip 333, are attached at the ends of the shaft 330. As best shown in FIGS. 10 and 11, the outer ends of the arms 232 are provided with adjustable stop bolts 336 which, when the tack seal operation is being performed, as will be described hereinafter in more detail, engage inwardly extending stop pieces 338 attached to the end members 318 and 319 of the tack seal carriage. When the tack seal is not in operative position, springs 340 pivot the arms 332 upwardly into the position illustrated in FIG. 9.

Independently mounted for rotation about the shaft 330 are second arms 342 which carry a transversely extending web guide member 344. As best shown in FIG. 10, the web is led from the last guide roll 312 in a downward and forward direction along the upper surface of the transverse guide strip 334 and then passes below the guide member 344. Attached to the guide member 334 is a series of spring fingers 346 which pass under and engage the web and hold it against the guide member 344. A desired relative adjustment between the guide member 344 and the resilient fingers 346 can be made by means of stop bolts 348 secured to the arms 342 and bearing against the upper surfaces of the arms 332.

As best shown to the right in FIG. 8, each of the arms 232 carries an inwardly extending plate 350 which is provided with an upwardly extending pin 352. Slidably mounted for vertical movement on the pins 352 is a transversely extending clamp piece mounting member 354. The mounting member 354 is resiliently held upwardly by springs 356 carried by the pins 352. Fastened to a pair of pins 358 extending vertically down through and slidable in the mounting member 354 is a clamp piece 360 which is urged downwardly by a spring 362. The lower surface of the member 360 carries a soft rubber clamping element 364 which, when the clamp piece is in operative position, as will be described hereinafter, holds the web against the guide member 334 to enable the web 204 to be pulled along with the tack seal unit as it moves longitudinally conjointly with the conveyor. The above-described spring mounting arrangement for the clamp piece 360 enables it to hold a desired pressure against the guide member 334 and to be retracted therefrom.

Each of the side frame members 318 and 319 is provided with a vertically disposed slot 370, as best shown in FIG. 10. The slots 370 receive pins extending outwardly from a sealing head support member 372, the slots and pins cooperating to hold the support member 372 is vertical alignment and permit it to slide vertically. Attached to the support member 372 by spring-loaded bolts 374 is a heated sealing head 376, uniform pressure by the head being afforded by the provision of a ball joint 378 between the mounting member 372 and the sealing bar 376a and the springs associated with the bolts 374 allowing pivotal motion of the head 376 with respect to the mounting member 372. The sealing bar 376a on the sealing head 376 is notched at intervals to enable the spring fingers 346 on the guide member 334 to be accommodated between the sealing bar and the surface of the tray flange when the tack seal operation is performed. In other words, the tack sealing tip 376a is arranged to provide the row of spaced-apart tack seals 34, illustrated in FIG. 1A, between the leading edge of the cover web and the leading flange of the package tray.

The elements of the web guide assembly and the tack seal head are operated by a cam bar 380 which, as best shown in FIG. 8, is mounted on a bracket 382 on the main machine frame. As shown by the phantom lines in FIGS. 9 and 10, the upper surface of the cam bar is disposed generally horizontally at a lower level for a first segment 380a and then curves smoothly into another substantially horizontal segment 38017 at an upper level. Aflixed at the outer end of a transversely extending shaft 382 rotatably mounted in the carriage frame members 318 and 319 is a cam follower 384 which is carried on a lever 386, and actuating arms 388 are attached to the shaft 382 inside of the carriage frame members 318 and 319. The outer ends of the arms 388 are held between adjustable bolts 390 extending downwardly from upper extensions on the sealing bar mounting member 372 and spring loaded pins 392 extending upwardly from lower extensions at the ends of the member 372. An intermediate point on one of the actuating arms 388 is engaged by a roller 394 carried by the clamp piece support member 354.

The tack seal mechanism operates in the following manner. When the web has been severed from the tray to which its leading edge was previously secured by the tack seal unit, the mechanisms of the tack seal are in the position illustrated in FIG. 9. More particularly, the carriage is in its rearward most position with respect to the movement of the conveyor, the clamp piece 360 is withdrawn from engagement with the web, the web guide members 334 and 344 are pivoted into a slightly raised position and the sealing bar 376 is retracted upwardly. This position is afforded by the location of the cam follower 384 along the lower horizontal section 380a of the cam bar 380.

The cycle of operation begins when the carirage begins to move forward. As will be described hereinafter the carriage is coupled to the cutting knife assembly and initial seal head and moves forwardly with these devices. During the initial period of forward movement of the tack seal unit, the cover web is being drawn back by the pullback unit so that it will be in the proper registration with the tray when the tack seal is formed. As the tack seal unit moves forwardly, the cam follower 384 traverses the curved portion of the cam bar and moves onto the upper horizontal surface 380b, causing the arms 388 to be pivoted in a counterclockwise direction, with respect to FIGS. 9 and 10. First, the roller 394 on the clamp piece frame 354 is engaged and the clamp 360 is pushed downwardly so that the web is gripped and held between it and the guide 334. Thereafter, the web is pulled forwardly along with the carriage with its leading edge in registration with the tray to which it will be 

